1. Field of the Invention
The present invention generally relates to a battery operated portable apparatus configured to provide respiratory ventilation in the far forward early trauma scene as well as in the clinical setting. Particularly, the invention is directed to a manifold/muffler assembly of a portable ventilator configured to provide smooth, constant airflow to the air recipient and to reduce the noise level associated with the cyclically operated compressor of the ventilator.
2. Description of Related Art
Respiration involves the introduction of gases, especially oxygen, to the lung during inspiration and the removal of waste gases, particularly carbon dioxide, during expiration. In healthy individuals respiration is normally effected by spontaneous ventilation or breathing, which results in the introduction of the necessary gases. Unfortunately, intentionally inflicted wounds or physiological and pathological processes may compromise normal pulmonary function leading to the inhibition of effective respiration or total respiratory failure. In such cases respiratory therapy, often involving artificial ventilation to some degree, is required.
For example, respiratory therapy is often necessary for victims of natural disasters or military actions associated with weapons of mass destruction, as well as for patients undergoing surgery or those suffering disorders and diseases of the pulmonary air passages. Typically, such respiratory therapy involves the use of mechanical ventilators.
Mechanical ventilators are simply devices that effect ventilation or, in other words, cause airflow into the lungs. More specifically, such devices typically force air into the lungs during the inspiration phase of the breathing cycle but allow a return to ambient pressure during spontaneous exhalation. The forced influx of fresh air by mechanical ventilation facilitates the pulmonary mediated processes that comprise respiration in mammals. One of these processes, the removal of waste gases, is the primary mechanism by which carbon dioxide is excreted from the body. Modern mechanical ventilators are designed to provide ventilation by regulating tidal volume (volume per breath), flow rate, delivery profile and respiratory flow thereby controlling carbon dioxide excretion. Because they can also regulate airway pressure and the concentration of inspired oxygen they offer control over oxygenation as well.
Numerous makes and models of mechanical ventilators are used today. All of the ventilators used are either volume-controlled ventilators or pressure-controlled ventilators. In the former, the ventilator is designed to deliver a set volume of gas regardless of the airway pressure. Such devices usually have a pressure cutoff to prevent damage to the lungs. In contrast, the pressure-controlled ventilators, based on the selected respiratory rate, the inspiratory gas flow and the peak airway pressure, deliver inspired gas, while monitoring the tidal volume, until the desired pressure is reached. Each of these types of mechanical ventilators incorporates a number of sophisticated features, which allow unparalleled control over the delivery of gases to the lung. In order to meet the diverse needs of patients requiring ventilation therapy, common mechanical ventilators offer several ventilation modes, each having a variety of programmable parameters, offering an almost unlimited versatility. Accordingly, both types of the above-discussed ventilators are highly expensive to manufacture and maintain.
Exemplifying at least some of the above-discussed principles of operation is U.S. Pat. No. 4,794,922 which discloses a ventilator operating in clinical conditions and configured to have an electronically controlled artificial respiration to a patient. The ventilator, as disclosed, features an air-tight manifold configured to house a system of ducts which provide air communication between the source of gas and the patient. While meeting many structural requirements, the ventilator of U.S. Pat. No. 4,794,922 is powered by an external source and, therefore, is not portable. Further, because of the complexity of the overall structure, the device is difficult to manufacture and is expensive.
A battery powered air mover or ventilator is known using “unfiltered” air supplies which generate acoustic noise and are characterized by a pulsatile flow, both of which can be quite disturbing to the air recipient. Mainly, these disadvantages stem from an unsatisfactory design of the gas-conveying and gas-storing components and particularly, the complexity of the internal tubing and the excess of the connectors needed to assemble the known ventilators. Particularly troublesome noise in the known ventilators is generated by a compressor cycled on and off to provide for the inspiration and expiration of the air recipient's lungs. When turned on, the loud noise produced by the compressor travels through the ventilation circuit tube and is heard by the air recipient. Critically, the configuration of the gas-conveying ducts and accumulators renders airflow entering the air-recipient's lungs pulsed. In addition, the number of elbows and tee connectors along the air path is characterized by multiple contractions and expansions in the flow area. As a consequence, the connectors creates the flow noise, which in combination with the pulsation, detrimentally affects audible and tactile senses of the patient during breathing.
Accordingly, a need exists for a light and compact field-portable ventilator configured to provide a constant, smooth flow of air towards a recipient thereof with a reduced level of noise produced by a compressor, as well as by airflow, typically associated with a battery-powered ventilator.